Method for laying a passable surface, for instance a playing ground, and surface thus formed

ABSTRACT

The invention relates to a method for laying a playable surface such as a playing field, comprising the steps of forming a hard substrate, arranging on the hard substrate a layer of resilient and/or damping material, and arranging a top layer on the resilient and/or damping layer, wherein during or after arranging of the hard substrate and/or the resilient and/or damping layer air chambers are formed therein. The behavior of the playing field becomes more natural due to these air chambers, and excessive resilience and energy restitution are avoided. The air chambers can be formed for instance by creating recesses in the relevant layer from the top, or by removing material from the layer at different locations after arranging thereof, for instance by melting or biological decomposition of inclusions. The invention also relates to a playing field obtain by application of this method.

The invention relates to a method for laying a playable surface, inparticular a playing field, comprising the steps of:

forming a relatively hard substrate,

arranging on the relatively hard substrate at least one layer of aresilient and/or damping material, and

arranging a top layer on the at least one layer of resilient and/ordamping material. Such a method is generally known and is applied onlarge scale to form playing fields, for instance synthetic turf fieldsfor sport and recreation. Synthetic turf fields are used particularlyfor playing ball sports such as football, American football, hockey andthe like.

In accordance with the known method a surface such as a synthetic turffield is formed by first forming a relatively hard, flat substrate, forinstance an asphalt layer, on the ground. A resilient and/or dampinglayer must then be arranged over this asphalt layer, because the fieldwould otherwise be too hard to play on, and would result in injuries toplayers. This resilient and/or damping layer can be arranged in the formof a mixture consisting of plastic or rubber granules or particles whichare held together by a binder, or in the form of solid material suppliedon rolls, for instance a closed or open-cell foam. The resilient and/ordamping material is arranged or unrolled on-site on the substrate,whereafter it is covered by the top layer, for instance a syntheticturf.

The known method has the drawback that the thereby formed playing fieldis often perceived as being too “bouncy” and has too great an energyrestitution. The behaviour of a ball is adversely affected by the largespring force of the resilient layer in the sense that a ball bounces toofast and too high compared to a natural turf. In addition, walking orrunning over such a resilient synthetic turf field is very tiring andunnatural.

The invention therefore has for its object to provide a method whichresults in a playing field, in particular a synthetic turf field, whichmore closely resembles a natural turf field than the synthetic turffields laid heretofore, which enables a better ball behaviour and whichdoes not result in excessive fatigue when playing on the field.According to the invention this is achieved in a method of the abovedescribed type in that, during or after arranging of the relatively hardsubstrate and/or the layer of resilient and/or damping material, airchambers are formed therein. As a result of the air chambers in thelayer of resilient and/or damping material, or even in the relativelyhard substrate, movements on the synthetic turf field are damped. Ballsfor instance hereby do not bounce too high, and walking or running overthe synthetic turf also feels natural. By further forming the airchambers during or after laying of the resilient and/or damping layer orthe hard substrate, these layers do not need to be manufactured fromspecially preprocessed material, and relatively simple, and thereforenot very costly materials can be used for this purpose.

A preferably applied variant of the method consists of the air chambersbeing formed in the relatively hard substrate and/or the layer ofresilient and/or damping material by creating recesses therein from thetop side after it is arranged. The arranging of recesses from the topcan be carried out quickly and with relatively simple means. Therecesses are preferably created by moving a machine provided withprotruding parts over the relatively hard substrate and/or the layer ofresilient and/or damping material. By using for instance a pressureroller provided with studs as machine, the recesses can be formedsimultaneously with pressing down of the substrate or resilient and/ordamping layer, whereby no additional operation is necessary.

In addition, it is also possible to create the recesses by pressing aprofiled mat into the layer of resilient and/or damping material. A matis here understood to mean any relatively thin closed material, forinstance a woven fabric, a non-woven, a foil and the like. A simple,smooth roller can in this case be used.

It is on the other hand also possible to envisage the air chambers beingformed in the layer of resilient and/or damping material by removingmaterial therefrom at different locations after the arranging thereof. Asimple method of forming the required air chambers in preciselycontrolled manner consists of inclusions of a material with low meltingpoint being arranged in the layer of resilient and/or damping materialwhich are removed by heating after the layer has been arranged.According to a variant, inclusions of a biologically degradable materialare arranged in the layer of resilient and/or damping material which areremoved by natural processes after the layer has been arranged. In thismanner the air chambers are created automatically after a period of timewithout any operations being necessary for this purpose.

According to yet another variant of the method according to theinvention, the air chambers are formed in the layer of resilient and/ordamping material during arranging thereof by including granules havinglarge dimensions relative to the thickness of the layer. The airchambers can thus be formed by replacing a part of the resilient and/ordamping material with material of a considerably larger size, wherebythe degree to which the resilient and/or damping layer is filled willdecrease greatly as a result of the poorer fit of the large granules,without additional operations being necessary for this purpose. In thatcase the layer of resilient and/or damping material can for instance bearranged in two steps, by first arranging a relatively flat adhesivelayer of material on the relatively hard substrate, and subsequentlyspreading the granules with large dimensions over the adhesive layer.

Finally, it is also conceivable for the air chambers to be formed in thelayer of resilient and/or damping material during arranging thereof byfirst laying a profiled mat on the relatively hard substrate, and byspreading the resilient and/or damping material over this mat. Such aprofiled mat in fact already contains the air chambers, so that theresilient and/or damping material need only be placed thereover andspread to form a layer which is flat on the upper side. Prior toarranging of the mat, heating wires can advantageously be receivedtherein, so that the mat can also serve as ground heating.

In the case use is made of a profiled mat, this mat can otherwise bemanufactured from a biologically degradable material or from a materialwith a low melting point. After forming of the playing field the mat canthus decompose in natural manner or be removed by heating.

In order to nevertheless form a very flat upper layer on which thesynthetic turf can be laid, this despite the presence of the airchambers, at least one other layer can also be arranged between thelayer with the air chambers and the synthetic turf. This layer can forinstance serve to distribute the load on the top layer uniformly intothe substrates, or can serve for additional resilience and/or damping.

When a synthetic turf is placed as top layer, a synthetic turf field isformed with the method according to the invention which has a verynatural feel.

At least some of the air chambers are advantageously connected to meansfor generating an air circulation therein. Warm air for instance canthus be blown under the playing field, whereby a simple and effectiveground heating is obtained.

The invention further relates to a playable surface, in particular aplaying field, comprising a relatively hard substrate, at least onelayer arranged thereon of a resilient and/or damping material, and a toplayer arranged in turn thereon. Such a surface, for instance in the formof a synthetic turf field, is likewise generally known, and has theabove discussed drawbacks.

The invention has for its object to further improve a playable surfaceof the stated type. According to the invention this is achieved in sucha surface by air chambers formed in the relatively hard substrate and/orthe layer of resilient and/or damping material.

Preferred embodiments of the playable surface according to the inventionare described in the dependent claims.

The invention is now elucidated on the basis of a number of embodiments,wherein reference is made to the annexed drawing, in which:

FIG. 1 is a schematic cross-section showing the structure of a prior artplaying field, and

FIG. 2 to 6 show corresponding cross-sections through differentembodiments of the playing field according to the invention.

A playable surface, for instance a prior art synthetic turf field 1(FIG. 1) is formed by a relatively hard substrate 2, for instance ofasphalt or stone chippings, over which a flat layer of resilient and/ordamping material 3 is arranged. This resilient and/or damping layer 3can have a thickness of about 10 to 40 mm. Arranged on the resilientand/or damping layer 3 is a top layer 4, here in the form of a syntheticturf consisting of a backing 5 and synthetic grass blades 6 connectedthereto by tufting, knitting or weaving.

The resilient and/or damping layer 3 can be formed in different ways. Itis for instance known to use a mixture of rubber granules 8 withrelatively small dimensions, in the order of several millimeters, forinstance 2-5 mm, which are mixed with a liquid binder, for instancepolyurethane. The thus formed mixture can then be spread over substrate2 using an asphalting machine or a paver specially developed for thepurpose. It is also possible on the other hand to use as resilientand/or damping material 3 a foam material which is supplied on rolls andsimply unrolled over the hard substrate 2.

As already indicated above, the known synthetic turf field 1 isexceptionally “bouncy” as a consequence of the presence of the layer ofresilient and/or damping material 3, whereby in the case of ball gamesthe bouncing behaviour of the ball is affected, which does not generallyenhance the quality of the game. The excessive resilience and energyrestitution of the synthetic turf field is moreover perceived by playersas being unpleasant and tiring.

So as to obviate these problems, it is proposed according to theinvention to form air chambers in the layer of resilient and/or dampingmaterial 3 or between the layer of resilient and/or damping material 3and the relatively hard substrate 2.

According to a first variant of the invention, the air chambers 17 areformed in the upper part of the layer of resilient and/or dampingmaterial 13 (FIG. 2). For this purpose recesses are formed from the topin the resilient and/or damping layer 13. These recesses can take arandom form, for instance be of circular cross-section. They arepreferably distributed uniformly over the surface of the synthetic turffield 11. When the resilient and/or damping layer 13 consists of amixture of rubber granules 18 and a binder, the recesses can be formedafter the resilient and/or damping layer 13 has been arranged on therelatively hard substrate 12, but before it has hardened. A machineprovided with protruding parts (not shown here) can for instance bemoved for this purpose over the not yet hardened resilient layer 13. Aprofiled pressure roller can be envisaged here, whereby the recessesthat will define the air chambers 17 are thus formed directly duringpressing down of the resilient and/or damping layer 13. In this mannerthe forming of air chambers 17 does not require a separate operatingrun.

According to a variant of this method, air chambers 17 are formed bylaying a profiled mat 20 on the resilient and/or damping layer 13 beforethis latter hardens, and by then pressing this mat 20 into the resilientand/or damping layer 13 (FIG. 3). Use can herein then be made of astandard roller or pressure roller without profile. Mat 20 can form apermanent part of the substrates, but could also be removed duringcuring of the resilient and/or damping layer. The mat could bemanufactured for this purpose from a material with low melting point,and could therefore be easily removed by heating. The use of abiologically degradable material for mat 20 can also be envisaged.

In the shown embodiment another layer 19 is otherwise also arrangedbetween the resilient and/or damping layer 13 and top layer 14, here inthe form of a pressure distribution layer of a relatively stiffmaterial, whereby the loads on top layer 14 are distributed evenly overthe resilient and/or damping layer 13, and subsidence of top layer 14 atthe position of air chambers 17 is prevented. A second flat resilientand/or damping layer could however also be arranged instead of apressure distribution layer 19.

Heating wires of a conductive material could further be included in mat20 or in the additional layer 19, which wires could be connected to oneor more electrical power supplies along the edge of the playing field.In this way the playing field 11 can be heated in simple manner, wherebyit remains readily playable, also in winter.

When the layer of resilient and/or damping material 13 is a foammaterial supplied on rolls, the recesses for the air chambers could beformed by local processing, either mechanically, thermally orchemically, of the upper side of the resilient and/or damping layer 13.

It is also possible to envisage the resilient and/or damping layer 13being formed by a mixture of rubber granules 18 and binder whichincorporates inclusions of a material which can be easily removed fromthe resilient and/or damping layer 13 after arranging thereof. It is forinstance possible to envisage inclusions of a material with a lowmelting point, such as polystyrene granules, which after arranging ofthe resilient and/or damping layer 13 can be removed by heating thislayer to above the melting point of the inclusions. Another possibilityis the use of inclusions of a biologically degradable material whichwill decompose automatically after a period of time, whereby airchambers are again formed in the resilient and/or damping layer 13. Theinclusions can herein be distributed over the whole layer 13, though itis also possible to envisage them being concentrated close to the topside, so that after heating or after decomposition of the material apattern is created as according to FIGS. 2 and 3.

In another embodiment of the synthetic turf field 21 according to theinvention (FIG. 4) the air chambers 27 are formed by intermediate spacesbetween relatively large granules 31 in the resilient and/or dampingmaterial. In the shown embodiment these granules 31 have dimensionswhich are almost the same as the thickness of the layer of resilientand/or damping material 23, although this is not always essential. Foran optimal effect however, the granules 31 do have to have dimensionswhich are relatively large in proportion to the thickness of the layerof resilient and/or damping material 23. It is possible to envisagedimensions amounting to more than half the thickness of the resilientand/or damping layer 23, preferably more than 70% thereof, and morepreferably more than 85% thereof. The resilient and/or damping layer 23can be formed in this embodiment by first arranging on the relativelyhard substrate 22 a relatively flat and thin adhesive layer 32 ofresilient and/or damping material, consisting for instance of a mixtureof relatively small granules 28 and binder or formed by a compact layerof polyurethane, and then scattering the relatively large granules 31 inthis adhesive layer 32. A synthetic turf 24 can then in turn be laid onthe relatively large granules 31, wherein on the top side of theresilient and/or damping layer 23 intermediate spaces are thus createdwhich will function as air chambers 27. Also shown here is a pressuredistribution layer 29 which, if desired, can be arranged between theresilient and/or damping layer 23 and top layer 24.

According to yet another variant of the invention the air chambers areformed by first laying on the relatively hard substrate 42 a profiled,at least initially form-retaining mat 50, the profile of which, togetherwith substrate 42, defines air chambers 47 (FIG. 5). Mat 50 can be awoven fabric with a mesh width smaller than the grain size of theresilient and/or damping material 48 which is spread over the profiledmat 50 and is finished to form a flat layer. A synthetic turf 44 canthen be arranged thereover. Heating wires can here also be incorporatedin mat 50.

In yet another embodiment of synthetic turf field 51 according to theinvention the air chambers 57 are likewise enclosed between therelatively hard substrate 52 and the resilient and/or damping layer 53,but are defined by recesses in the relatively hard substrate 52, whilethe resilient and/or damping layer 53 is substantially flat. Therecesses in the upper part of the relatively hard substrate 52 can beformed in the same manner as the recesses in the resilient and/ordamping layer 13 according to the first embodiment. A pressuredistributing layer 59 can here optionally also be arranged between therelatively hard substrate 52 and the resilient and/or damping layer 53.A synthetic turf 54 is in turn laid on the flat layer of resilientand/or damping material 53, which in the shown embodiment consists of aplastic foam.

Although not show here, air chambers 17, 27, 47, 57 could be connectedto means for generating an air circulation therein. These circulationmeans could be formed by one or more fans or compressors along the edgeof the playing field with which air could be blown through air chambers17, 27, 47, 57. If this air is first heated, a simple system of groundheating is thus created.

The layer of resilient and/or damping material can, as stated, consistof a mixture of rubber granules and a binder such as polyurethane. Inaddition to the rubber granules, other plastic materials can also beused such as polystyrene granules, polyethylene foam, rubber foam,polyurethane foam and the like. In addition, use could be made in smallpart of stone chippings, thereby considerably reducing the cost of theresilient and/or damping layer.

Although the invention is elucidated above with reference to a number ofembodiments, it will be apparent that it is not limited thereto, andthat many modifications and adjustments are possible within the scope ofthe following claims. A further flat layer of resilient and/or dampingmaterial could for instance be arranged between the layer of resilientand/or damping material with the air chambers and the relatively hardsubstrate. In addition, the different variants of the layers with airchambers could be combined for an even better damping. The form anddimensions of the air chambers, their number and the distributionthereof over the playing field can further be varied as desired so as toarrive at the required degree of damping. Finally, other playingsurfaces, such as floors of sports halls, athletic tracks and the like,can also be envisaged for application of the invention instead ofsynthetic turf fields. Even other types of surfaces suitable for walkingon, such as floors in industrial premises or homes, could be providedwith air chambers with the purpose of increasing comfort.

The scope of the invention is therefore defined solely by the claims.

The invention claimed is:
 1. A playable surface, comprising: arelatively hard substrate with a horizontal, flat top surface, at leastone layer arranged thereon of a resilient and/or damping material, and atop layer arranged in turn thereon, wherein permanent air chambers areformed in the at least one layer of resilient and/or damping materialduring or after arranging of the at least one layer of resilient and/ordamping material, wherein a profiled mat is arranged between therelatively hard substrate and the at least one layer of resilient and/ordamping material and over which the resilient and/or damping material isspread, wherein the air chambers take the form of recesses in the lowerpart of the at least one layer of resilient and/or damping materialdefined by the profile of the mat, the profile mat being manufacturedfrom biologically degradable material or from a material with a lowermelting point than the resilient and/or damping material, and whereinthe air chambers are embedded only in the at least one layer ofresilient and/or damping material and do not extend below the topsurface of the relatively hard substrate.
 2. The surface as claimed inclaim 1, wherein the permanent air chambers comprise spaces formed byremoving inclusions in the layer of resilient and/or damping material.3. The surface as claimed in claim 1, wherein the top layer is asynthetic turf.
 4. The surface as claimed in claim 1, further comprisinga device connected to at least some of the permanent air chambers, forgenerating an air circulation therein.
 5. The surface as claimed inclaim 1, wherein heating wires are received in the mat.
 6. The surfaceas claimed in claim 1, wherein the air chambers are embedded in the atleast one layer of resilient and/or damping material such that theyexist above the top surface of the relatively hard flat substrate. 7.The surface as claimed in claim 1, wherein the air chambers are embeddedin the at least one layer of resilient and/or damping material such thatthey vertically project from the top surface of the relatively hard flatsubstrate.